.\" SPDX-License-Identifier: BSD-2-Clause
.\" Copyright (C) 2019 - 2020 Intel Corporation.
.\"
.TH "MEMKINDALLOCATOR" 3 "2019-09-24" "Intel Corporation" "MEMKINDALLOCATOR" \" -*- nroff -*-
.SH "NAME"
libmemkind::static_kind::allocator<T> \- The C++ allocator compatible with the C++ standard library allocator concepts
.br
.BR Note:
.I memkind_allocator.h
functionality is considered as stable API (STANDARD API).
.SH "SYNOPSIS"
.nf
.B #include <memkind_allocator.h>
.sp
.B Link with -lmemkind
.sp
.BI "libmemkind::static_kind::allocator(libmemkind::kinds " "kind" );
.br
.BI "template <typename U> libmemkind::static_kind::allocator<T>::allocator(const libmemkind::static_kind::allocator<U>&)" " "noexcept;
.br
.BI "template <typename U> libmemkind::static_kind::allocator(const allocator<U>&& " "other" ) " "noexcept;
.br
.BI "libmemkind::static_kind::allocator<T>::~allocator();
.br
.BI "T *libmemkind::static_kind::allocator<T>::allocate(std::size_t " "n" ) " "const;
.br
.BI "void libmemkind::static_kind::allocator<T>::deallocate(T " "*p" ", std::size_t " "n" ) " "const;
.br
.BI "template <class U, class... Args> void libmemkind::static_kind::allocator<T>::construct(U " "*p" ", Args... " "args" ) " "const;
.br
.BI "void libmemkind::static_kind::allocator<T>::destroy(T " "*p" ) " "const;
.fi
.SH "DESCRIPTION"
The
.BR libmemkind::static_kind::allocator<T>
is intended to be used with STL containers to allocate from static kinds memory. Memory management is based on memkind library. Refer
.BR memkind (3)
man page for more details.
.PP
The
.BR libmemkind::kinds
specifies allocator static kinds of memory, representing type of memory which offers different characteristics. The available types of allocator kinds of memory:
.PP
.B libmemkind::kinds::DEFAULT
Default allocation using standard memory and default page size.
.PP
.B libmemkind::kinds::HUGETLB
Allocate from standard memory using huge pages. Note: This kind requires huge pages configuration described in
.B SYSTEM CONFIGURATION
section.
.PP
.B libmemkind::kinds::INTERLEAVE
Allocate pages interleaved across all NUMA nodes with transparent huge pages disabled.
.PP
.B libmemkind::kinds::HBW
Allocate from the closest high bandwidth memory NUMA node at the time of allocation. If there is not enough high bandwidth memory to satisfy the request, errno is set to ENOMEM and the allocated pointer is set to
.IR "NULL" .
.PP
.B libmemkind::kinds::HBW_ALL
Same as
.B libmemkind::kinds::HBW
except decision regarding closest NUMA node is postponed until the time of first write.
.PP
.B libmemkind::kinds::HBW_HUGETLB
Same as
.B libmemkind::kinds::HBW
except the allocation is backed by huge pages. Note: This kind requires huge pages configuration described in
.B SYSTEM CONFIGURATION
section.
.PP
.B libmemkind::kinds::HBW_ALL_HUGETLB
Combination of
.B libmemkind::kinds::HBW_ALL
and
.B libmemkind::kinds::HBW_HUGETLB
properties. Note: This kind requires huge pages configuration described in
.B SYSTEM CONFIGURATION
section.
.PP
.B libmemkind::kinds::HBW_PREFERRED
Same as
.B libmemkind::kinds::HBW
except that if there is not enough high bandwidth memory to satisfy the request, the allocation will fall back on standard memory.
.PP
.B libmemkind::kinds::HBW_PREFERRED_HUGETLB
Same as
.B libmemkind::kinds::HBW_PREFERRED
except the allocation is backed by huge pages. Note: This kind requires huge pages configuration described in
.B SYSTEM CONFIGURATION
section.
.PP
.B libmemkind::kinds::HBW_INTERLEAVE
Same as
.B libmemkind::kinds::HBW
except that the pages that support the allocation are interleaved across all high bandwidth nodes and transparent huge pages are disabled.
.PP
.B libmemkind::kinds::REGULAR
Allocate from regular memory using the default page size. Regular means general purpose memory from the NUMA nodes containing CPUs.
.PP
.B libmemkind::kinds::DAX_KMEM
Allocate from the closest persistent memory NUMA node at the time of allocation. If there is not enough memory in the closest persistent memory NUMA node to satisfy the request,
.I errno
is set to
.B ENOMEM
and the allocated pointer is set to
.IR "NULL" .
.PP
.B libmemkind::kinds::DAX_KMEM_ALL
Allocate from the closest persistent memory NUMA node available at the time of allocation. If there is not enough memory on any of persistent memory NUMA nodes to satisfy the request,
.I errno
is set to
.B ENOMEM
and the allocated pointer is set to
.IR "NULL" .
.PP
.B libmemkind::kinds::DAX_KMEM_PREFERRED
Same as
.B libmemkind::kinds::DAX_KMEM
except that if there is not enough memory in the closest persistent memory NUMA node to satisfy the request, the allocation will fall back on other memory NUMA nodes.
.BR Note:
For this kind, the allocation will not succeed if two or more
persistent memory NUMA nodes are in the same shortest distance to the same CPU on which process is eligible to run.
Check on that eligibility is done upon starting the application.
.PP
All public member types and functions correspond to standard library allocator concepts and definitions. The current implementation supports C++11 standard.
.PP
Template arguments:
.br
.I T
is an object type aliased by value_type.
.br
.I U
is an object type.
.PP
.BR Note:
.br
.BI "T *libmemkind::static_kind::allocator<T>::allocate(std::size_t " "n")
allocates memory using
.BR memkind_malloc ().
Throw
.I std::bad_alloc
when:
.RS
.I n
= 0
.RE
.br
.RS
.br
or there is not enough memory to satisfy the request.
.RE
.PP
.BI "libmemkind::static_kind::allocator<T>::deallocate(T " "*p" ", std::size_t " "n")
deallocates memory associated with pointer returned by
.BR allocate ()
using
.BR memkind_free ().
.SH "SYSTEM CONFIGURATION"
Interfaces for obtaining 2MB (HUGETLB) memory need allocated
huge pages in the kernel's huge page pool.
.TP
.B HUGETLB (huge pages)
Current number of "persistent" huge pages can be read from
.I /proc/sys/vm/nr_hugepages
file.
Proposed way of setting hugepages is:
.BR "sudo sysctl vm.nr_hugepages=<number_of_hugepages>" .
More information can be found here:
.UR https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt
.UE
.SH "COPYRIGHT"
Copyright (C) 2019 - 2020 Intel Corporation. All rights reserved.
.SH "SEE ALSO"
.BR memkind (3)
